The superior thyroid artery arises from the

external carotid artery The external carotid artery is the major artery of the head and upper neck. It arises from the common carotid artery. It terminates by splitting into the superficial temporal and maxillary artery within the parotid gland. Structure Origin T ...

just below the level of the greater cornu of the

hyoid bone The hyoid-bone (lingual-bone or tongue-bone) () is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid-cartilage. At rest, it lies between the base of the mandible and the third cervical verte ...

and ends in the

thyroid gland The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans, it is a butterfly-shaped gland located in the neck below the Adam's apple. It consists of two connected lobes. The lower two thirds of the lobes are connected by ...

Structure

From its origin under the anterior border of the

sternocleidomastoid The sternocleidomastoid muscle is one of the largest and most superficial cervical muscles. The primary actions of the muscle are rotation of the head to the opposite side and flexion of the neck. The sternocleidomastoid is innervated by the acces ...

the superior thyroid artery runs upward and forward for a short distance in the

carotid triangle The carotid triangle (or superior carotid triangle) is a portion of the anterior triangle of the neck. Anatomy Boundaries It is bounded: * Posteriorly by (the anterior border of) the sternocleidomastoid muscle, * Anteroinferiorly by (the sup ...

, where it is covered by the skin,

platysma The platysma muscle or platysma is a :wikt:superficial, superficial muscle of the human neck that overlaps the sternocleidomastoid. It covers the anterior surface of the neck superficially. When it contracts, it produces a slight wrinkling of the ...

, and

fascia A fascia (; : fasciae or fascias; adjective fascial; ) is a generic term for macroscopic membranous bodily structures. Fasciae are classified as superficial, visceral or deep, and further designated according to their anatomical location. ...

; it then arches downward beneath the

omohyoid The omohyoid muscle is a muscle in the neck. It is one of the infrahyoid muscles. It consists of two bellies separated by an intermediate tendon. Its inferior belly is attached to the scapula; its superior belly is attached to the hyoid bone. Its i ...

sternohyoid The sternohyoid muscle is a bilaterally paired, long, thin, narrow strap muscle of the anterior neck. It is one of the infrahyoid muscles. It is innervated by the ansa cervicalis. It acts to depress the hyoid bone. The sternohyoid muscle is a ...

, and

sternothyroid The sternothyroid muscle (or sternothyroideus) is an infrahyoid muscle of the neck. It acts to depress the hyoid bone. Structure The two muscles are in contact with each other proximally (close to their origin), but diverge distally (towards t ...

muscles. To its medial side are the

inferior pharyngeal constrictor muscle The inferior pharyngeal constrictor muscle is a skeletal muscle of the neck. It is the thickest of the three outer pharyngeal muscles. It arises from the sides of the cricoid cartilage and the thyroid cartilage. It is supplied by the vagus nerve ...

and the external branch of the

superior laryngeal nerve The superior laryngeal nerve is a branch of the vagus nerve. It arises from the middle of the inferior ganglion of the vagus nerve and additionally receives a sympathetic branch from the superior cervical ganglion. The superior laryngeal nerve ...

Branches

It distributes twigs to the adjacent muscles, and numerous branches to the

, connecting with its fellow of the opposite side, and with the inferior thyroid arteries. The branches to the gland are generally two in number. One, the larger, supplies principally the anterior surface; on the isthmus of the gland it connects with the corresponding artery of the opposite side. A second branch descends on the posterior surface of the gland and anastomoses with the

inferior thyroid artery The inferior thyroid artery is an artery in the neck. It arises from the thyrocervical trunk and passes upward, in front of the vertebral artery and longus colli muscle. It then turns medially behind the carotid sheath and its contents, and a ...

. Besides the arteries distributed to the muscles and to the thyroid gland, the branches of the superior thyroid are: *The infrahyoid branch (or hyoid artery): a small artery that runs along the lower border of the

beneath the

thyrohyoid muscle The thyrohyoid muscle is a small skeletal muscle of the neck. Above, it attaches onto the greater cornu of the hyoid bone; below, it attaches onto the oblique line of the thyroid cartilage. It is innervated by fibres derived from the cervical spin ...

. This artery connects with the infrahyoid branch of the opposite side. The infrahyoid branch is a derivative of the

second The second (symbol: s) is a unit of time derived from the division of the day first into 24 hours, then to 60 minutes, and finally to 60 seconds each (24 × 60 × 60 = 86400). The current and formal definition in the International System of U ...

aortic arch The aortic arch, arch of the aorta, or transverse aortic arch () is the part of the aorta between the ascending and descending aorta. The arch travels backward, so that it ultimately runs to the left of the trachea. Structure The aorta begins ...

. *The sternocleidomastoid branch runs downward and laterally across the sheath of the

common carotid artery In anatomy, the left and right common carotid arteries (carotids) () are artery, arteries that supply the head and neck with oxygenated blood; they divide in the neck to form the external carotid artery, external and internal carotid artery, inte ...

, and supplies the

sternocleidomastoideus The sternocleidomastoid muscle is one of the largest and most superficial cervical muscles. The primary actions of the muscle are rotation of the head to the opposite side and flexion of the neck. The sternocleidomastoid is innervated by the acces ...

muscle and neighboring muscles and skin; it frequently arises as a separate branch from the

. * The superior laryngeal artery accompanies the

internal laryngeal branch The superior laryngeal nerve is a branch of the vagus nerve. It arises from the middle of the inferior ganglion of the vagus nerve and additionally receives a sympathetic branch from the superior cervical ganglion. The superior laryngeal nerve ...

of the

, beneath the

. This artery branches from the superior thyroid artery near its bifurcation from the

. Together with the

internal laryngeal nerve The superior laryngeal nerve is a branch of the vagus nerve. It arises from the middle of the inferior ganglion of the vagus nerve and additionally receives a sympathetic branch from the superior cervical ganglion. The superior laryngeal nerve ...

, it pierces the lateral thyrohyoid membrane, and supplies blood to the muscles,

mucous membrane A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It ...

, and glands of the

larynx The larynx (), commonly called the voice box, is an organ (anatomy), organ in the top of the neck involved in breathing, producing sound and protecting the trachea against food aspiration. The opening of larynx into pharynx known as the laryngeal ...

, connecting with the branch from the opposite side. *The cricothyroid artery may contribute to the supply of the larynx. It follows a variable course either superficial or deep to the

sternothyroid muscle The sternothyroid muscle (or sternothyroideus) is an infrahyoid muscle of the neck. It acts to depress the hyoid bone. Structure The two muscles are in contact with each other proximally (close to their origin), but diverge distally (towards t ...

. If superficial, it may be accompanied by branches of the

ansa cervicalis The ansa cervicalis (or ansa hypoglossi in older literature) is a loop formed by muscular branches of the cervical plexus formed by branches of cervical spinal nerves C1-C3. The ansa cervicalis has two roots - a superior root (formed by branch o ...

, and if deep, it may be related to the

external laryngeal nerve The superior laryngeal nerve is a branch of the vagus nerve. It arises from the middle of the inferior ganglion of the vagus nerve and additionally receives a sympathetic branch from the superior cervical ganglion. The superior laryngeal nerve p ...

. It can connect with the artery of the opposite side and with the laryngeal arteries.

Clinical significance

This artery must be ligated at the thyroid when conducting a

thyroidectomy A thyroidectomy is an operation that involves the surgery, surgical removal of all or part of the thyroid gland. In general surgery, endocrine or head and neck surgeons often perform a thyroidectomy when a patient has thyroid cancer or some other ...

. If the artery is severed, but not ligated, it will bleed profusely. In order to gain control of the bleeding, the

surgeon In medicine, a surgeon is a medical doctor who performs surgery. Even though there are different traditions in different times and places, a modern surgeon is a licensed physician and received the same medical training as physicians before spec ...

may need to extend the original incision laterally to ligate the artery at its origin at the

. Furthermore, the external laryngeal branch of the superior laryngeal nerve courses close to the superior thyroid artery, making it at risk of injury during surgery.

Additional images

File:Gray474.png, Diagram showing the origins of the main branches of the carotid arteries. File:Gray513.png, The internal carotid and vertebral arteries. Right side. (Superior thyroid visible at center.) File:Gray1174.png, The thyroid gland and its relations. File:Gray1210.png, Side of neck, showing chief surface markings. File:Slide3jjj.JPG, Superior thyroid artery File:Slide1EBAB.JPG, Muscles, arteries and nerves of neck.Newborn dissection. File:Slide2deded.JPG, Muscles, nerves and arteries of neck.Deep dissection. Anterior view.

References

External links